火灾下基于纤维梁和分层壳模型的结构破坏机制分析

Collapse Mechanism Analysis of Structures under Fire Based on the Fiber Beam and Layered Shell Models

为分析混凝土空间框架结构在火灾下的反应规律及其破坏机理,基于已建立的纤维梁单元和混凝土分层壳单元的火灾破坏数值模型,通过在截面层次上来考虑构件截面的不均匀温度场分布及其材料非线性和几何非线性,并引入纤维梁单元截面形心结点与分层板壳单元结点的偏离以及位移协调条件来建立两者的连接模型,从而实现考虑楼板作用的整体结构火灾反应分析模型.最后,运用建立的模型对两个多层框架进行了火灾反应分析,分析了楼板和梁柱的相互作用规律及其破坏机制.结果表明,纤维梁单元模型和分层壳模型能够用于模拟钢筋混凝土结构的受火破坏过程,并且火灾发生的位置不同,结构的破坏机制也不同.

In order to analyze the response and collapse mechanism of spacial concrete frame structures under fire,a numerical model of the whole structure under fire based on the fiber beam model and layered shell model was proposed.By dividing the cross section of beam element into many small fibers and the cross section of shell element into concrete and steel layers,and considering the eccentricity and displacement compatibility conditions between the fiber beam centroid and the layered shell node,this model could consider the non-uniform temperature distribution across the section and simulate the behavior of material nonlinearity and geometry nonlinearity.Based on this model,the response and collapse mechanism of a multi-story reinforced concrete structure was analyzed.The results showed that this fiber model and layered shell model could be used to simulate the collapse process of reinforced concrete frames under fire,and different fire scenarios leaded to different collapse mechanisms.